Design and adaptation of a folded split ring resonator antenna for an animal borne sensor

Dodson, Samuel Christopher Keightley (2018-03)

Thesis (MEng)--Stellenbosch University, 2018.


ENGLISH ABSTRACT: This thesis describes the selection, design, adaptation and construction of a folded split ring resonator (FSRR) antenna to replace the existing transmitting antenna in an animal-borne behavioural monitoring system (ABBMS). The antenna is required to fit completely inside a small rectangular enclosure of dimension 105 x 65x 26 mm, which is attached to the rear leg of a rhinoceros. An FSRR antenna is selected from a group of candidate antennas based on its high radiation and re ection efficiencies erad and eref , quasi-isotropic radiation pattern, small electrical size and availability of impedance tuning mechanisms. A prototype model is designed and optimised in FEKO simulation software and is manufactured on FR-4 substrate. It is then compared to a similar FSRR design from the literature and is found to behave similarly, even though the substrate on which our prototype is constructed is more affordable. The prototype is then adapted to fit inside the enclosure. The prototype antenna is reduced from a 3-dimensional to a planar form to incorporate a small surface mount balun. The planar model is transformed from a circular shape to a rectangular shape, and a thicker FR-4 substrate is included. The length and breadth of the antenna are set to 103:5 mm and 63:5 mm respectively. These transformations reduce the eref and erad values. However, the model now fits inside the enclosure. The feed of the rectangular model is subsequently inverted to face inward, to allow the incorporation of sensor electronics onto the antenna's substrate in the future. This further decreases eref . The eref is increased by adjusting the inner-feed antenna's tuning parameters. The resulting model is constructed and compared to the first circular prototype. It is shown to operate with higher eref and it also maintains the quasi-isotropic radiation pattern. However, the thick FR-4 substrate decreases the erad. This decreases the realised gain below the requirement. It is recommended to use a low loss substrate, of a similar permittivity, to alleviate this.

AFRIKAANSE OPSOMMING: Hierdie proefskrif beskryf die keuse, ontwerp, aanpassing en konstruksie van 'n gevoude verdeelring resonator (FSRR) antenna om die bestaande transmissie antenna in 'n dier-gemonteerde gedragsmoniteringstelsel (ABBMS) te vervang. Die antenna word benodig om binne 'n klein reghoekige omhulsel van afmetings 105 x 65x 26 mm te pas, wat aan die agterbeen van 'n renoster gekoppel is. 'n Sirkelvormige FSRR-antenna word gekies uit 'n lys kandidaat-antennas, gebaseer op sy hoë stralings en weerkaats-doeltreëndheid erad en eref , kwasiisotropiese stralingspatroon, klein elektriese grootte en beskikbaarheid van impedansie-aanpassingsmeganismes. 'n Optimale prototipe model is ontwerp in FEKO simulasie sagteware en is vervaardig met FR-4 substraat. Dit vergelyk goed met 'n soortgelyke FSRR-ontwerp, selfs al is die substraat waarop ons prototipe gebou is, meer bekostigbaar. Die prototipe word dan aangepas om binne die omhulsel te pas. Die 3-dimensionele prototipe antenna word verminder tot 'n planêre vorm sodat 'n klein oppervlak-gemonteerde balun daarop ingewerk kan word. Die prototipe word omskep van 'n sirkelvorm na 'n reghoekige vorm wat 'n dikker FR-4-substraat bevat. Die lengte en breedte van die antenna word onderskeidelik gestel op 103:5 mm en 63:5 mm. Die transformasies verminder die eref en erad van die antenna. Die model pas egter nou in die omhulsel. Die voer van hierdie model word dan omgekeer om na binne te wys, sodat sensorelektronika in die toekoms op die antenna se substraat geïntegreer kan word. Dit verminder verder eref . Die eref word verhaal deur toepaslike verandering aan die reghoekige antenna se aanpassingsparameters. Die gevolglike model is vervaardig en vergelyk met die eerste prototipe en toon `n hoër eref . Dit handhaaf ook die kwasi-isotropiese stralingspatroon. Die dikker substraat waarop dit gedruk is, verminder egter die erad. Dit verminder die gerealiseerde aanwinste benede die vereistes. Dit word aanbeveel om 'n lae-verlies substraat, van 'n soortgelyke permittiwiteit, te gebruik om dit te verlig.

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